Tsv via provided with a stress release structure and its fabrication method

ABSTRACT

A TSV via structure comprising an upper part made on the side of the front face of a substrate in which electronic components are located and a lower part with height and cross-section smaller than the height and cross-section the upper part, the arrangement of the connection element in the substrate being such that it releases stresses generated by the different materials of said structure.

TECHNICAL FIELD

The invention relates to the field of microelectronic and/or nano-electronic and microsystems and/or nanosystems and particularly the field of vertical interconnection structures commonly called TSV (Through Silicon Vias) passing through a semiconducting substrate.

It allows for the use of a microelectronic and/or nano-electronic device provided with a vertical TSV interconnection structure with an improved shape and arrangement so as to limit stresses induced by materials forming this structure on the remainder of the device.

PRIOR ART

TSV type vias can be used during the manufacture of electronic devices comprising a plurality of stacked substrates or chips to pass through the thickness of one or several of these substrates or these chips.

TSV vias can be used to make a connection between a conducting element located on a face called “front face” or the side of the front face of a substrate and another conducting element located on another face called the “back face” or the side of the back face of said substrate.

Several families of methods for making a TSV vias exist depending on whether the vias are made before or after or at the same time as the electronic components to be interconnected.

In a method of the type commonly called “via first”, the TSV vias are made before the electronic components on the substrate, particularly before the transistors.

In a method of the type commonly called “via middle”, the TSV vias are made after components are made but before the electric connections of these components.

In a method of the type commonly called the “via last”, the TSV vias are made after the fabrication of electronic components and their connections to an external device.

TSV vias are formed by filling at least one hole passing through a semiconducting support using a conducting material. The coefficient of thermal expansion of the metallic material that fills the hole is usually very different from that of the semiconducting support.

When the filling material is made of Cu, the coefficient of thermal expansion may for example be of the order of 18 ppm/° C. whereas the coefficient of thermal expansion of an Si based support may for example be of the order of 2.6 ppm/° C.

Furthermore, in the case in which the vias are filled subsequently by means of a passivation polymer to insulate the metallic material from the support material, this expansion effect is also amplified because the filling polymers have even higher coefficients of expansion, for example between 60 and 180 ppm/° C.

A large difference in coefficients of thermal expansion can cause high mechanical stresses within a microelectronic device, these stresses possibly causing particularly separation or delamination of the metallic material or a failure of contact continuity zones formed on the front face and the back face of a substrate. The typical order of magnitude of stresses that must not be exceeded is usually of the order of 100 MPa, for a stress of more than 500 MPa that can cause rupture.

The document entitled “Development and characterisation of high electrical performances TSV for 3D applications”, D. Henry et al. EPTC Conference 2009 discloses a method for making a TSV via structure formed from a metallic connection element lining the walls of a hole passing through the substrate.

In this method, the via hole is made through the back face of the substrate so as to open up directly on a metallic zone to be connected without making any contact continuity on the front face of the substrate.

Document EP 0363256 B1 discloses a TSV via structure formed by laser etching from the back face of a substrate.

This structure is formed from a metallic connection element lining the walls of a hole passing through the substrate. During the substrate etching step, its front face is protected by means of a layer providing protection against splashes caused by etching. This protection layer may possibly be conducting and it can also be used to maintain continuity of the contact on the front face.

The document entitled “Enabling 3d-IC foundry technologies for 28 nm node and beyond: TSV integration with high throughput die-to-wafer stacking” D. Y. chen et al. TSMC, IEDM09-353 discloses a method for making a TSV via by etching the front face of a substrate.

Document US 2010/0264548 discloses a method for making a TSV via in two parts in which an upper part of a connection element is formed by making small holes through the front face of a substrate which are subsequently filled by means of a metallic material, and another larger hole is then made through the back face and a metallic material is deposited lining the walls of this other hole.

The method disclosed in this document requires that several steps are done to achieve contact continuity on the front face.

The problem arises of finding a new TSV via structure with less strict stress phenomena, and a new method of making such a structure.

PRESENTATION OF THE INVENTION

This invention applies firstly to a method of making an interconnection structure comprising steps to:

-   -   form a first hole through a first face of a support on which one         or several electronic components are or will be made, the first         hole partially passing through the support and having a critical         dimension D₁ and a height H₁,     -   make an upper part of a conducting connection element by the         formation of a conducting material in said first hole so as to         cover the walls and the bottom of said first hole, a central         zone in the first hole not being filled by said metallic         material,     -   form at least one second hole through a second face of the         support opposite said first face, said second hole being made         along a prolongation of the first hole and opening up on said         upper part of said connection element, said second hole also         being formed so as to have a critical dimension D₂<D₁ and a         height H₂<H₁,     -   make a lower part of said conducting connection element by the         formation of a conducting material in said second hole so as to         cover the walls and the bottom of the second hole, a central         zone of said second hole not being filled by said conducting         material.

Such a method can be used to make a via in which the stresses are limited.

After making the upper part and before formation of said second hole(s), the method may also comprise the formation of a layer of a given material on said second face of the support, designed such that said given material has a Young's modulus and a coefficient of thermal expansion higher than the Young's modulus and the coefficient of thermal expansion of the support, respectively.

Such a layer can limit stresses.

According to one possible embodiment of the method, the critical dimension D₁, the critical dimension D2 and the height H₂, may be selected such that (D1−D2)/H2>4.

According to one possible embodiment of the method, an insulating material can be formed before said upper part of the said connection element is formed so as to line the bottom and the walls of said first hole. Formation of said second hole may then comprise etching of the support as far as said insulating material, the method also comprising the following, before formation of said lower part of said connection element:

-   -   formation of an insulating material so as to line the walls and         bottom of said second hole,     -   etching of the bottom of the second hole of said insulating         materials, so as to prolong said second hole and expose said         upper part of said connection element.

After the formation of said upper part of said conducting connection element and before formation of said second hole(s), there may be a step to thin the support on the side of said second face of the support.

According to one possible embodiment of the method, the second hole may have a height H₂ such that H₂<H₁/10.

According to one possible embodiment of the method, the diameter D₂ of the second hole may be such that D₂≦0.5*D₁.

Such aspect ratios can limit stresses within the via.

According to one possible embodiment of the method, said central zone of said first hole may be filled with an insulating material after said upper part of said conducting connection element has been made.

Said insulating filling material of said central zone of the first hole may be selected to have a lower coefficient of thermal expansion than said conducting material lining the walls and the bottom of the first hole, so as to reduce stresses in the via.

According to one possible embodiment of the method, after said lower part of said conducting connection element has been made, said central zone of said second hole may be filled with an insulating material.

In order to reduce stresses within the via, said insulating filling material of said central zone of the second hole may have a lower coefficient of thermal expansion than said conducting material covering the walls and bottom of the second hole.

According to one possible embodiment of the method, production of said upper part of said conducting connection element may comprise the formation of a conducting zone extending on or parallel to the first face of the support.

After said lower part of said conducting connection element has been made, the method may include the formation of a zone of said conducting material extending on or parallel to the second face of the support.

This invention also relates to an interconnection structure comprising a conducting connection element provided with:

-   -   an upper part opening up on a first face of a support on which         one or several electronic components are made or will be made,         the upper part being made in a first hole partially passing         through said support and having a critical dimension D₁ and a         height H₁, said upper part being formed from a conducting         material covering the walls and the bottom of a first hole, a         central zone in the first hole not being filled with said         conducting material,     -   a lower part connected to said upper part and opening up on a         second face of the support opposite the first face, the lower         part being made in one or several second hole(s) communicating         with the first hole and partially passing through said support,         the second hole(s) having a critical dimension D₂<D₁ and height         H₂<H₁, said lower part being formed from a conducting material         covering the walls and the bottom of the second hole(s), a         central zone of said second hole(s) not being filled by said         conducting material.

According to one possible embodiment of the structure, a layer based on a given material with a Young's modulus and a higher coefficient of thermal expansion than the Young's modulus and coefficient of thermal expansion of the support, may be provided on the second face of the support.

For example, the given material may be AlN or TiW.

According to one possible embodiment of the structure, the central zone of said first hole and/or second hole may be filled with an insulating material.

According to one possible embodiment of the structure, the coefficient of thermal expansion of the insulating material filling the central zone of said first hole and/or second hole may be lower than that of said conducting material.

According to one possible embodiment of the structure, the critical dimension D₁, the critical dimension D2 and the height H₂ may be selected such that (D1−D2)/H2>4.

According to one possible embodiment of the structure, the height H₂ of said second hole(s) may be such that H₂<H₁/10.

According to one possible embodiment of the structure, the diameter D₂ of said second hole(s) may be such that D₂≦0.5*D₁.

According to one possible embodiment of the structure in which said upper part of said metallic connection element comprises a conducting zone extending on or parallel to the first face of the support, said lower part of said conducting connection element may comprise a conducting zone extending on or parallel to the second face of the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

This invention will be better understood after reading the description of example embodiments given purely for information and in no way limitative, with reference to the appended drawings in which:

FIG. 1 shows an example interconnection structure according to the invention, this structure comprising a connection element passing through a support and being configured so as to limit mechanical stress phenomena induced by the component materials,

FIGS. 2A-2B show means of releasing applied mechanical stresses within a TSV type interconnection structure used according to the invention,

FIGS. 3A-3H show different example embodiments of the lower part of a TSV type interconnection structure according to the invention,

FIGS. 4A-4P show an example of a method according to the invention for making a TSV type interconnection structure,

FIGS. 5A-5C show an example of the method according to the invention for making a variant TSV type interconnection structure used according to the invention.

Identical, similar or equivalent parts of the different figures are marked with the same numeric references in order to facilitate comparison between different figures.

The different parts shown in the figures are not necessarily all shown at the same scale, to make the figures more easily understandable.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

An example interconnection structure according to the invention will now be presented with reference to FIG. 1.

This is a TSV (Through Silicon Via) type structure that passes through a substrate 100 that may be semiconducting and for example based on Si and have a thickness for example between 100 μm and 300 μm, or for example between 10 μm and 100 μm.

This structure is formed from a metallic connection element 110 that may for example be based of copper and may comprise an upper part 112 made in a first hole 104 passing partially through the substrate 100 and opening up on the side of a face of the substrate called the “front face”.

The front face of the substrate 100 is a face on which one or several electronic components C_(i) such as transistors are arranged (the set of components C_(i) being diagrammatically represented by a box in discontinuous lines in FIG. 1).

The upper part 112 of the connection element 110 is formed from a metallic zone 112 a lining the bottom and walls of the first hole 104 and at least one other metallic zone 112 b extending on the front face of the substrate 100 or parallel to the front face of the substrate 100 and it may act as a contact continuity zone.

The first hole 104 is also filled at its centre with a zone made of material 111 with a lower coefficient of thermal expansion than the metallic material of said upper part 112 of the connection element 110. This material 111 may be insulating and for example be made of polymer such as Benzocyclobutene (BCB).

The metallic connection element 110 also comprises a lower part 142 made in at least one second hole 134 communicating with the first hole 104 and opening up on the side of the face of the substrate called the “back face”, opposite the first face.

The lower part 142 of the connection element 110 is formed of a metallic zone 142 a lining the bottom and the walls of the second hole 134 and at least one other metallic zone 142 b extending on the back face of the substrate 100 or parallel to the back face of the substrate 100. This other metallic zone 142 b may act as a contact continuity zone.

The second hole 134 is also filled at its centre with a material 141 that has a lower coefficient of thermal expansion than the metallic material of said lower part 142 of the connection element 110. This material 141 may be insulating and for example it may be based on a polymer such as Benzocyclobutene (BCB).

The walls of the first hole 104 and the second hole 134 are covered with a thickness e₁ and e₂ respectively of a dielectric material in order to electrically isolate the connection element 140 from the substrate 100.

The first hole 104 and the second hole 134 may be vertical.

The first hole 104 in which the upper part of the connection element is formed has a critical dimension D₁ (measured along a direction parallel to the [O;{right arrow over (i)};{right arrow over (k)}] plane in the [O;{right arrow over (i)};{right arrow over (j)};{right arrow over (k)}] orthogonal coordinate system in FIG. 1) and a height H₁ or depth H₁ (measured along a direction parallel to vector {right arrow over (j)} [O;{right arrow over (i)};{right arrow over (j)};{right arrow over (k)}] in the orthogonal coordinate system in FIG. 1). Throughout this description, “critical dimension” means the smallest dimension of an element, or a pattern, or a zone, other than its thickness or its height.

The second hole 134 has a critical dimension D₂ (measured along a direction parallel to the [O;{right arrow over (i)};{right arrow over (k)}]) plane and a height H₂ or a depth H₂ (measured along a direction parallel to the vector {right arrow over (j)}).

The first hole 104 and the second hole 134 are selected such that H₂<H₁ and D₂<D₁, to limit stresses within the interconnection structure.

The first hole 104 may be made such that its height H₁ is at least ten times more than the height H₂ of the second hole 134. The first hole 104 may be made such that its section is larger than the section of the second hole 134, and in particular such that the critical dimension D₁ of the first hole 104 is 4 times greater than the critical dimension D₂ of the second hole 134.

Thus, due to the dimension of the holes 104 and 134, substrate zones 100 around the lower part 142 and under the upper part 112 of the metallic connection element 110, may form bars or beams 101 with a large aspect ratio, i.e. length to thickness ratio, to enable a spring or damping effect of stresses within the interconnection structure.

The thickness e_(p) of the beams 101 depends particularly on the height H₂ of the lower part 142 of the connection element and it may be of the order of the difference between H₂ and the thickness e₁ of the insulating layer separating the connection element 110 from substrate 100 at the bottom of the first hole 104.

The length l_(p) of the beams 101 under the lower part 142 of the connection element 140 depends on the difference between the critical dimension D₁ of the first hole 104 and the critical dimension D₂ of the second hole 134. The length l_(p) may be of the order of the difference (D₁+e₁)−(D₂+e₂) between the accumulated distance (D₁+e₁) of the critical dimension D₁ and the thickness e₁ of the insulating layer separating the upper part 112 of the connection element 110 from the substrate 100 at the bottom of the first hole 104, and the accumulated distance (D₂+e₂) of the critical dimension D₂ and the thickness e₂ of the insulation layer separating the lower part 142 of the connection element 110 from the substrate 100 at the walls of the second hole 134.

For example, in the case in which d₁≈e₂, the ratio (D₁−D₂)/H₂ may for example be equal to at least 4 to enable a large reduction in the stresses.

The arrangement of the connection element in the form of zones lining the walls of the first hole 104 and the second hole 134 gives good mechanical strength and also contributes to limiting the stresses in the interconnection structure.

The first hole 104 may also be made so that it comprises a bottom with rounded edges 104 a. This can also contribute to reducing stresses in the interconnection structure.

FIGS. 2A-2B show an example layout under the upper part 142 of a metallic connection element 110 of an interconnection structure, in a bottom view (FIG. 2A) and along a longitudinal section A′A (shown in FIG. 2B).

The upper part 112 of the connection element 110 is supported by zones of the substrate 100 forming beams 101 under the rounded edges of the first hole 104, the aspect ratio of these beams 101 being selected to release stresses induced by the metallic material.

Different example embodiments of the lower part 142 of the metallic connection element of a TSV type interconnection structure are shown in FIGS. 3A-3H.

In the example in FIGS. 3A and 3C, the lower part of the connection element comprises several metallic zones 242 a, 242 c formed in the holes 234 a, 234 c respectively, in the form of a cylinder of revolution, the walls of which are covered by an insulating material and the centre of which is also filled with insulating material.

In the examples in FIGS. 3B and 3H, the holes 234 b, 234 h in which the metallic zones 242 a, 242 h forming the lower part of the connection element have a rectangular parallelepiped shape.

According to other examples shown in FIGS. 3D and 3G, the lower part of the metallic connection element comprises several discontiguous metal zones 242 d, 242 g arranged in the vertical holes 234 d, 234 g passing partially through a substrate and with curved walls, the holes being arranged relative to each other so that their cross-sections are in the shape of a ring, or several concentric rings.

According to another example embodiment shown in FIG. 3E, the lower part of the metallic connection element comprises a metallic zone 242 e arranged in a hole 234 e, the cross-section of which forms a contour in a saw tooth pattern.

According to another example embodiment shown in FIG. 3F, the lower part of the metallic connection element comprises a metallic zone 242 f arranged in a hole 234 f with a comb-shaped cross-section.

One example embodiment of a TSV interconnection structure according to the invention will now be described with reference to FIGS. 4A-4P.

In this example, the initial material may be a semiconducting substrate 100, for example based on Si and with a thickness for example of between 100 μm and 300 μm, covered on one of its faces called the “front face” with an insulating layer 101 that may for example be based of SiO₂ and with a thickness for example of the order of 500 nm.

One or several electronic components such as transistors may already have been made on the front face of the substrate 100.

The first step is to form a first hole 104 in part of the thickness of the substrate 100. The first hole 104 may be vertical (the vertical direction being a direction parallel to vector {right arrow over (j)} in the [O;{right arrow over (i)};{right arrow over (j)};{right arrow over (k)}] orthogonal coordinate system in FIG. 4A) and it may have a depth H₁ (measured along a direction parallel to vector {right arrow over (j)}) for example between 100 μm and 300 μm and a diameter or a critical dimension D₁ (the critical dimension or the diameter being measured along a direction parallel to the [O;{right arrow over (i)};{right arrow over (k)}] plane in the [O;{right arrow over (i)};{right arrow over (j)};{right arrow over (k)}]) orthogonal coordinate system for example between 30 μm and 100 μm.

Throughout this description, the “critical dimension” of an element or a pattern or a zone means the smallest dimension of this element or this pattern or this zone, apart from its thickness or height or its depth (measured along a direction parallel to vector {right arrow over (j)} in the [O;{right arrow over (i)};{right arrow over (j)};{right arrow over (k)}] orthogonal coordinate system in FIG. 4A).

A second insulating layer 105 can then be formed on the walls and the bottom of the first hole 104, continuous with the first insulating layer 101.

This may for example be done by thermal oxidation of the semiconducting material of the substrate 100 or by deposition, for example SACVD (Sub-Atmospheric Pressure Chemical Vapour Deposition) or LPCVD (Low Pressure Chemical Vapour Deposition). The second insulating layer 105 may for example be chosen to have a thickness e₁ approximately equal to the thickness of the insulating layer 101 covering the front face of the substrate 100 and for example between 10 nm and 10 μm.

The next step (FIG. 4B), is to deposit a so-called “growth” layer 107 on the front face of the substrate 100 so as to cover the insulating layer 101 and to line the walls and the bottom of the first hole 104. This growth layer 107 may be formed from a bi-layer, for example comprising a sub-layer based on Ti and a sub-layer of Cu deposited for example by PVD (Physical Vapour Deposition). According to another possibility, the bi-layer may for example be formed based on TiN and Cu and may be deposited for example by CVD (Chemical Vapour Deposition). The growth layer 107 is selected to encourage growth of a metallic material for example such as Cu on the walls and at the bottom of the hole 104.

Thus, the next step is to form a layer of metallic material 109 so as to partially fill the first hole 104. This filling is done so as to line the bottom and the walls of the first hole 104, and it may be done so as to cover the zones of the front face of the substrate 100 located close to the opening of the first hole 104. Partial filling of the first hole 104 is done such that a zone located at the centre of the first hole 104 is not filled with metallic material. The metallic material may for example be Cu and it may be formed by an ECD (Electrochemical Deposition) method. The thickness of the layer of metallic material 109 made may for example be of the order of 10 μm. This thus forms an upper part 112 of a vertical connection element 110 or via in the first hole 104.

The next step is to remove the growth layer 107 in zones located on the front face of the substrate 100 and around the upper part 112 of the vertical connection element 110. This may be done for example by wet chemical etching using H₂SO₄ or HF (FIG. 4C).

The next step is to form a layer 111 based on a material with a lower coefficient of thermal expansion than the materials 107 and 109, so as to fill the central zone of the hole 104 and cover the front face of the substrate 100. This layer 111 may be insulating. For example, this insulating layer 111 may be based on polymer and may be made so as to cover the metallic layer 109 and fill the hole 104. The polymer material of the insulating layer 111 may for example be Benzocylcobutene (BCB). The insulating thickness 111 may for example be between 10 μm and 30 μm (FIG. 4D).

The next step is to make an opening 113 in the insulating layer 111 exposing a zone of the metallic layer 109 supported on the front face of the substrate 100 (FIG. 4E).

The next step is to form a metallic connection pad 116 in this opening 113, for example based on Cu or formed from a stack of metallic layers covered with a Cu layer. The connection pad 116 may for example have a height (measured along a direction parallel to vector {right arrow over (j)} in the [O;{right arrow over (i)};{right arrow over (j)};{right arrow over (k)}] orthogonal coordinate system in FIG. 4F) of between 10 μm and 30 μm.

The next step is to form a handle layer 121 on the front face of the substrate 100. This handle layer 121 may for example be based on glass or silicon and assembled to the substrate 100 through a glue layer 119 for example based on a polymer that may be a thermoplastic material with adhesive properties. The thickness of the glue layer 119 may for example be between 100 μm and 1000 μm (FIG. 4G).

The substrate 100 can then be thinned by the removal of a portion of the substrate 100 located on the side of the face called the “back face” which is opposite the front face.

This thus reduces the distance d between the bottom of the first hole 104 and the back face of the substrate 100. The thickness of the substrate 100 that is removed may for example be between 100 μm and 1000 μm.

Thinning may be done such that the distance d (measured along a direction parallel to vector {right arrow over (j)} of the [O;{right arrow over (i)};{right arrow over (j)};{right arrow over (k)}] orthogonal coordinate system in FIG. 4H) separating the bottom of the first hole 104 and the back face of the substrate 100 is less than 20 μm or less than or equal to 10 μm.

The back face of the substrate 100 may then be covered by an insulating layer 131 that may for example be based on SiO₂ and made by deposition or by oxidation.

The next step is to form a second hole 134 in part of the thickness of the substrate 100 facing the first hole 104. This second hole 134 may be made so as to open up onto the insulating layer 105 lining the bottom of the first hole 104. The second hole 134 may for example be made by etching using KOH (FIG. 4I).

The height H₂ and cross-section of the second hole 134 are smaller than the height and cross-section of the first hole 104.

The second hole 134 may be selected with a depth H₂ (measured along a direction parallel to vector {right arrow over (j)} in the [O;{right arrow over (i)};{right arrow over (j)};{right arrow over (k)}]) orthogonal coordinate system) of less than 20 μm or preferably less than or equal to 10 μm. The second hole 134 is thus made with a lower height H₂ than the first hole 104, and with a diameter or critical dimension D₂ (the critical dimension or the diameter being measured along a direction parallel to the [O;{right arrow over (i)};{right arrow over (k)}] plane in the [O;{right arrow over (i)};{right arrow over (j)};{right arrow over (k)}] orthogonal coordinate system in FIG. 4I) for example between 1 μm and 50 μm and smaller than the critical dimension D₁ of the first hole 104.

Another insulating layer 135 continuous with the insulating layer 131 can then be formed on the walls and the bottom of the second hole 134. This can be done for example by thermal oxidation of the semiconducting material of the substrate 100, particularly when the insulating layer 135 is based on SiO₂. According to another possibility (FIG. 4J), the insulating layer 135 may be based on polymer such as for example BCB. This other insulating layer 135 may have a thickness e₂ for example between 10 nm and 10 μm.

The next step is to remove the insulating layer 135 at the bottom of the second hole 134 and the portion of the insulating layer 105 lining the bottom of the first hole 104. This removal may be done for example using RIE (Reactive Ion Etching) type dry etching, for example based on CF₃—O₂. This exposes a metallic zone of the upper part 112 of the metallic connection element (FIG. 4K).

Another metallic “growth” layer 137 can then be formed on the back face of the substrate 100 so as to cover the insulating layer 131 and to line the walls of the second hole 134. This other growth layer 137 may also be made at the bottom of the second hole 134. The growth layer 137 may be formed from a bi-layer, for example based on Ti and Cu or based on TiN and Cu (FIG. 4L).

The next step is to form a layer of metallic material 139 so as to partially fill the second hole 134 and to line the bottom and the walls of this second hole, and possibly to cover zones of the back face of the substrate 100 located close to the opening of the second hole 134.

Partial filling of the second hole 134 is thus made such that a zone located at the centre of the second hole 134 is not filled with the metallic material (FIG. 4M). The metallic filling material 139 may for example be Cu. This is how the lower part 142 of the vertical connection element is made.

The central zone of the second hole 134 is then also filled so as to close it off with a material 141 with a smaller coefficient of thermal expansion than the metallic material(s) lining the walls of the second hole 134. The material 141 may be insulating so as to make a passivation layer on the back face of the substrate 100. For example, the insulating material 141 may be a polymer material such as BCB. The thickness of the passivation layer may for example be between 0.5 μm and 20 μm.

The next step is to make an opening 143 in the passivation layer 141 exposing a zone 142 b in the lower part 142 of the vertical connection element supported on the back face of the substrate 100 (FIG. 4N).

The next step is to form a metallic connection pad 146 in this opening 143, for example based on Cu or formed from a stack of metallic layers covered by a Cu layer (FIG. 4O).

The handle layer 121 is then removed for example through removal by shearing (FIG. 4P).

FIGS. 5A-5C show a variant of the method for making an interconnection structure like that described above with reference to FIGS. 4A-4P.

For this variant, after the thinning step described with reference to FIG. 4H, the back face of the substrate 100 is covered by a layer 231 that may be based on a material with a high coefficient of thermal expansion (CTE), for example more than 20 ppm/° C. and a high Young's modulus for example higher than 150 GPa. The layer 231 may in particular be chosen to be based on a material with a higher coefficient of thermal expansion and a higher Young's modulus than the material in the substrate 100 on which this layer 231 is deposited.

For example, the layer 231 may be based on AlN or TiW, and its thickness may for example be between 1 μm and 20 μm, preferably of the order of 2 μm or 3 μm.

The second hole 134 is then formed in a part of the thickness of the substrate 100 facing the first hole 104. This second hole 134 may be made so as to open up on the insulating layer 105 lining the bottom of the first hole 104 (FIG. 5A).

An insulating layer 135 may then be formed on the walls and the bottom of the second hole 134, for example based on polymer for example such as BCB (FIG. 5B).

Steps similar to those described above with reference to FIGS. 4K to 4M are then performed, consisting of removing the insulating layer 135 from the bottom of the second hole 134 and the insulating layer 105 from the bottom of the first hole 104 so as to expose the metallic layer 107 at the bottom of the first hole 104, and then to form the layer of metallic material 139, the insulating material 141, and the connection pad 146. 

1: A method for fabricating an interconnection structure comprising: forming a first hole through a first face of a support on which one or several electronic components are or will be made, the first hole partially passing through the support and having a critical dimension D₁ and a height H₁, making an upper part of a conducting connection element by the formation of a conducting material in said first hole so as to cover the walls and the bottom of said first hole, a central zone in the first hole not being filled by said metallic material, forming one or several second hole(s) through a second face of the support opposite said first face, said second hole(s) being made along the prolongation of the first hole and opening up on said upper part of said connection element, said second hole(s) also being formed so as to have a critical dimension D₂<D₁ and H₂<H₁, making a lower part of said conducting connection element by the formation of a conducting material in said second hole(s) so as to cover the walls and the bottom of the second hole(s), a central zone of said second hole(s) not being filled by said conducting material, the method further comprising the formation of a layer of a given material on said second face of the support after making an upper part and before formation of said second hole(s), said given material having a Young's modulus and a coefficient of thermal expansion higher than the Young's modulus and the coefficient of thermal expansion of the support, respectively. 2: A method according to claim 1, the critical dimension D₁, the critical dimension D2, the height H₂, being selected such that (D1−D2)/H2>4. 3: A method according to claim 1, wherein an insulating material is formed before the formation of said upper part of said connection element, so as to line the bottom and the walls of said first hole, and in which the formation of the second hole comprises etching of the support as far as said insulating material, the method also comprising the following, before formation of said lower part of said connection element: formation of an insulating material so as to line the walls and bottom of said second hole, etching of the bottom of the second hole(s) of said insulating materials, so as to prolong said second hole(s) and expose said upper part of said connection element. 4: A method according to claim 1, further comprising a step of thinning the support on the side of said second face of the support, after said formation of said upper part of said conducting connection element and before formation of said second hole(s). 5: A method according to claim 1, said second holes(s) having a height H₂ such that H₂<H₁/10. 6: A method according to claim 1, said second holes(s) having a diameter D₂ such that D₂≦0.5×D₁. 7: A method according to claim 1, wherein said central zone of said first hole is filled with an insulating material after said upper part of said conducting connection element has been made. 8: A method according to claim 7, said insulating filling material of said central zone of the first hole(s) having a lower coefficient of thermal expansion than said conducting material covering the walls and bottom of the first hole(s). 9: A method according to claim 1, wherein said central zone of said second hole(s) is filled with an insulating material after said lower part of said conducting connection element has been made. 10: A method of making an interconnection structure according to claim 9, said filling insulating material of said central zone of the second hole(s) having a lower coefficient of thermal expansion than said conducting material covering the walls and bottom of the second hole(s). 11: A method according to claim 1, wherein production of said upper part of said conducting connection element comprises the formation of a conducting zone extending on or parallel to the first face of the support. 12: A method according to claim 1, wherein said production of said lower part of said conducting connection element comprises the formation of a zone of said conducting material extending on or parallel to the second face of the support.
 13. An interconnection structure having a conducting connection comprising: an upper part opening up on a first face of a support on which one or several electronic components are made or will be made, the upper part being made in a first hole partially passing through said support and having a critical dimension D₁ and a height H₁, said upper part being formed from a conducting material covering the walls and the bottom of a first hole, a central zone in the first hole not being filled with said conducting material, a lower part connected to said upper part and opening up on a second face of the support opposite the first face, the lower part being made in one or several second hole(s) communicating with the first hole and partially passing through said support, the second hole(s) having a critical dimension D₂<D₁ and height H₂<H₁, said lower part being formed from a conducting material covering the walls and the bottom of the second hole(s), a central zone of said second hole(s) not being filled by said conducting material, a layer of a given material supported on said second face of the support, said given material having a Young's modulus and a higher coefficient of thermal expansion than the Young's modulus and coefficient of thermal expansion of the support. 14: An interconnection structure according to claim 13, the central zone of said first hole and/or second hole being filled with an insulating material. 15: An interconnection structure according to claim 13, the coefficient of thermal expansion of the insulating material filling the central zone of said first hole and/or second hole is lower than that of the conducting material covering the walls of the first and the second hole. 16: An interconnection structure according to claim 13, the critical dimension D₁, the critical dimension D2 and the height H₂, being selected such that (D1−D2)/H2>4. 17: An interconnection structure according to claim 13, the height H₂ of said second hole(s) is such that H₂<H₁/10. 18: An interconnection structure according to claim 13, the diameter D₂ of said second hole(s) is such that D₂≦0.5*D₁ 19: A interconnection structure according to claim 13, wherein said upper part of said metallic connection element comprises a conducting zone extending on or parallel to the first face of the support, said lower part of said conducting connection element comprising a conducting zone extending on or parallel to the second face of the substrate. 